﻿using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;

namespace CYTS.Aoyou.Framework.Utility
{
    /// <summary>
    /// 对称加密算法
    /// </summary>
    public class SymmetricEncrypt
    {
        private static SymmetricAlgorithm mobjCryptoService = new RijndaelManaged();

        /// <summary>
        /// 密钥
        /// </summary>
        private const string Key = "CYTS";

        /// <summary>
        /// 获得密钥
        /// </summary>
        /// <returns>密钥</returns>
        private static byte[] GetLegalKey()
        {
            string sTemp = Key;
            mobjCryptoService.GenerateKey();
            byte[] bytTemp = mobjCryptoService.Key;
            int KeyLength = bytTemp.Length;
            if (sTemp.Length > KeyLength)
                sTemp = sTemp.Substring(0, KeyLength);
            else if (sTemp.Length < KeyLength)
                sTemp = sTemp.PadRight(KeyLength, ' ');
            return ASCIIEncoding.ASCII.GetBytes(sTemp);
        }

        ///<summary>
        ///获得初始向量IV
        ///</summary>
        ///<returns>初试向量IV</returns>
        private static byte[] GetLegalIV()
        {
            string sTemp = "CYTS";
            mobjCryptoService.GenerateIV();
            byte[] bytTemp = mobjCryptoService.IV;
            int IVLength = bytTemp.Length;
            if (sTemp.Length > IVLength)
                sTemp = sTemp.Substring(0, IVLength);
            else if (sTemp.Length < IVLength)
                sTemp = sTemp.PadRight(IVLength, ' ');
            return ASCIIEncoding.ASCII.GetBytes(sTemp);
        }

        ///<summary>
        ///加密方法
        ///</summary>
        ///<param name="Source">待加密的串</param>
        ///<returns>经过加密的串</returns>
        public static string Encrypto(string Source)
        {
            byte[] bytIn = UTF8Encoding.UTF8.GetBytes(Source);
            MemoryStream ms = new MemoryStream();
            mobjCryptoService.Key = GetLegalKey();
            mobjCryptoService.IV = GetLegalIV();
            ICryptoTransform encrypto = mobjCryptoService.CreateEncryptor();
            CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Write);
            cs.Write(bytIn, 0, bytIn.Length);
            cs.FlushFinalBlock();
            ms.Close();
            byte[] bytOut = ms.ToArray();
            return Convert.ToBase64String(bytOut);
        }

        ///<summary>
        ///解密方法
        ///</summary>
        ///<param name="Source">待解密的串</param>
        ///<returns>经过解密的串</returns>
        public static string Decrypto(string Source)
        {
            byte[] bytIn = Convert.FromBase64String(Source);
            MemoryStream ms = new MemoryStream(bytIn, 0, bytIn.Length);
            mobjCryptoService.Key = GetLegalKey();
            mobjCryptoService.IV = GetLegalIV();
            ICryptoTransform encrypto = mobjCryptoService.CreateDecryptor();
            CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Read);
            StreamReader sr = new StreamReader(cs);
            return sr.ReadToEnd();
        }
    }
}
